Method of coating with metals and resulting products



- vegetable, animal, and mineral oils, but also- Patented Dec. 8, 1925.,

p UNITED STATES PATENT OFFICE.

ARTHUR Z. PEDERSEN, OF WEST ORANGE, NEW JERSEY, ASSIGNOR, IBY MESNE AS- SIGNMENTS, T0 MADSENELL CORPORATION, OF NEW YORK, N. Y.,. A. CORPORA- TION OF NEW YORK.

METHOD OF COATING WITH MYI'AIIS AND RESULTING PRODUCTS.

No Drawing. Application filed May 14, 1920, Serial No. 381,435. Renewed November 10, 1828.

To all whom it"may concern:

'Be it known that I, ARTHUR Z. PEDERS-EN, a citizen of the United States, and a resident of the town of \Vest Orange, county of Essex, State of New Jersey, have invented an Improvement in Methods of Coating with Metals and Resulting Products, of which the following is a specification.

My invention relates to improvements in methods of preparing metallic surfaces'for receiving adherent coatings of metal and to the products resulting from such improved methods. My invention is particularly applicable in coating iron or steel articles with another metal, such as nickel, whether by electro-deposition, fusion, or otherwise.

By way of illustration, I shall describe my invention as applied to the coating of iron or steel surfaces with nickel by any of the usual or well-known methods of electrodepositing nickel. It is, however, to be understood that my invention is not limited to this particular application which is herein set forth by way of example only.

I have discovered that by employing the surface of the metallic ob'ect to be coated as an anode in strong sulp uric acid, a new and unexpected result is obtained which renders the subsequent metallic coating remarkably adherent and gives toit certain other desirable qualities,jas, freedom from blistering on heating, and the like, of considerable practical and commercial importance. I prefer to employ sulphuric acid of more than about 75%, usually of more than about 85%, strength. In particular, I find that anhydrous, or substantially anhydrous, sulphuric acid is very desirable for the treatment of-the surface of a steel object preparatory to receiving a coating of another metal, such as nickel. During this operation there is very little gassing, very little of the metal is eaten away, and no undesirable odor is generated. a

The above operation not only cleansthe surface very thoroughly, removing grease,

brings about a condition of the surface thus treated which renders the coatings unusually sound and adherent. The exact cause of this phenomenon is not clear, and I do not wish to be limited to any particular theory or explanation of the action of the strong sulwhat is known in the art as an electric cleaner in which the object whose surface is to be prepared for receiving a metallic coating is so connectedas to serve as the anode, while, for the cathode, I use either another piece of steel, orpreferably a sheet of lead.

The electrical characteristics of such a cell are peculiar and unusual. Preferably, I employ a line voltage of less than about 42 volts, since if the line voltage equals or exceeds about 42 volts, excessive arcing takes place which may injure the article bein treated and may have other undesirable e fects. Assuming, for example, a line voltage of about 20 volts, there is initiallj a flow of current amounting to about 30 amperes per square foot, where either anhydrous, or substantially anhydrous sulphuric acid or 66 Baum sulphuric acid, that is, sulphuric acid approximately 96% strong, is employed in the bath. For a few seconds the current density drops slightly,'then there is momentarily a sudden and slight increase. in current density, after which the current density continues to continuall about ten minutes, w en the operation is complete, and when the current density will diminish until after.

be found to be generally less than one ampare per square foot, or even nearly zero. his condition constitutin a substantial condition of equilibrium in t e cell after the period of time set forth above, i dicates that equal to t e polarization voltage of the cell, in this case apparently 20 volts.

As a result of the treatment set forth, even where the surface is initially coated with the volta e impressed on the ce 1 isat least grease and oxide, the treated surface, after a brief shaking in water, is found to be of a clean gray metallic lustre, which receives the metallic coating readily. The coating is found to be remarkably adherent and the object will be found not to readily blister or separate from its coating on heating, or in use.

It is of course, to be understood that my invention is not limited to the particular embodiment thereof herein set forth by way I of example merely.

What I claim is:

1. The method of preparing metallic surfaces to receive adherent metallic coatings which comprises making the object to be coated the anode in a bath containing sulphuric acid of more than about 75% stren th.

2. The method of preparing metallic surfaces to receive adherent metallic coatings which comprises making the object to be coated the anode in a bath containing sulphuric acid of more than about 85% stren th.

3. The method of preparing metallic surfaces to receive adherent metallic coatings which comprises making the object to be coated the anode in a bath containing substantially anhydrous sulphuric acid.

larization balance voltage of the cell.

5. The method of preparing metallic surfaces to receive adherent metallic coatings Which comprises making the object to be coated the anode in a bath containing substantially anhydrous sulphuric acid, and impressing on the cell thus formed a voltage at least equal to the polarization balance 3 voltage of the cell.

In testimony whereof, I have signed my name to this specification this eleventh day of May, 1920.

ARTHUR Z. PEDERSEN. 

